The currently used radiographic contrast materials, which are salts of tri-iodinated derivatives of benzoic acid, often produce adverse clinical reactions. A new, substantially less toxic compound, Metrizamide, which contains glucosamine residue, is nonionic. Because of the hydrolyzability of the sugar amide bond, however, it is unstable. Under this grant we developed a synthetic approach for attaching polyhydroxyl substituents to the tri-iodophenyl moiety in a way which results in compounds of high stability and, in some instances, lower toxicity than Metrizamide. We propose to synthesize and systemically test a number of representatives of this new class which should yield nonionic, highly water soluble and stable media. We further intend to synthesize and characterize oligomers of such compounds. From previous data on similar compounds, we expect the nonionic oligomers to have low neural toxicity. Toxicity of all new compounds will be determined in protozoan cultures, by their i.v. LD50 in mice, and by their effect on brain electrical activity of rabbits, following instillation into the cisterna magna.